Anti-thrombogenic venous shunt system and method

ABSTRACT

A venous shunt system and method adapted to shunt cerebral spinal fluid in a patient. A fluid control device having a fluid passage is adapted to be placed allowing cerebral spinal fluid to flow through the fluid passage. A catheter having a lumen, the catheter being in fluid communication with the fluid control device. At least a portion of at least one of the catheter and the fluid control device being subjected to an anti-thrombogenic treatment.

FIELD OF THE INVENTION

The present invention relates generally to the field of venous shuntsystems and method and, more particularly, to venous shunt systems andmethods used for treating hydrocephalus.

BACKGROUND OF THE INVENTION

Ventricles of the brain contain cerebrospinal fluid which cushions thebrain against shock. Cerebral spinal fluid is constantly being secretedand absorbed by the body usually in equilibrium. Cerebral spinal fluidis produced in the ventricles of the brain, where under normalconditions, it is circulated in the subarachnoid space and reabsorbedinto the bloodstream, predominantly via the arachnoids villi attached tothe superior sagittal sinus. However, if blockages in circulation ofcerebral spinal fluid, perhaps in the ventricles, cerebral spinal fluidcan't be reabsorbed by the body at the proper rate.

This can create a condition known as hydrocephalus which is a conditionmarked by an excessive accumulation of fluid violating the cerebralventricles, then the brain and causing a separation of the cranialbones. Hydrocephalus is a condition characterized by abnormal flow,absorption or formation of cerebrospinal fluid within the ventricles ofthe brain which subsequently increases the volume and pressure of theintracranial cavity. If left untreated, the increased intracranialpressure can lead to neurological damage and may result in death.

A common treatment for hydrocephalus patients has been the cerebrospinalfluid shunt. The standard shunt consists of the ventricular catheter, avalve and a distal catheter. The excess cerebrospinal fluid is typicallydrained from the ventricles to a suitable cavity, most often theperitoneum or the atrium. The catheter is placed into ventricles toshunt cerebral spinal fluid to other areas of the body, principally theperitoneum or alternatively to the sagittal sinus, where it can bereabsorbed. The presence of the shunt relieves pressure from cerebralspinal fluid on the brain.

A problem with venous shunt systems and methods is the possiblecomplication of thrombus formation. A thrombus may form, for example, inthe lumen of the shunting catheter or on the surface of the catheter.The same is true for a fluid flow device, e.g., a pressure or flowregulator, which may be included in the venous shunt system. Further,thrombus formation may occur near the area of the outlet tip thecatheter, the so-called tip zone.

Formation of thrombus in or near the venous shunt system, whether in oron a component of the venous shunt system, could lead to blockage offlow and compromise the performance of the shunt system.

BRIEF SUMMARY OF THE INVENTION

Clogging or occluding of a venous shunt system may be prevented orcorrected through the use of an anti-thrombogenic and/or clot bustingagent or agents. The use of such agent or agents can be effective inpreventing the formation of a thrombus or in the elimination of athrombus already formed.

In a preferred embodiment, the present invention provides a venous shuntsystem adapted to shunt cerebral spinal fluid in a patient. A catheter,having a lumen, is adapted to be placed allowing cerebral spinal fluidto flow through the lumen. At least a portion of the catheter beingsubjected to an anti-thrombogenic treatment.

In another embodiment, the present invention provides a venous shuntsystem adapted to shunt cerebral spinal fluid in a patient. A fluidcontrol device having a fluid passage is adapted to be placed allowingcerebral spinal fluid to flow through the fluid passage. A catheterhaving a lumen, the catheter being in fluid communication with the fluidcontrol device. At least a portion of at least one of the catheter andthe fluid control device being subjected to an anti-thrombogenictreatment.

In a preferred embodiment, the anti-thrombogenic treatment comprises ananti-thrombogenic agent delivered to a proximate area of at least one ofthe catheter and the fluid control device.

In a preferred embodiment, a bioresorbable matrix holds theanti-thrombogenic agent.

In a preferred embodiment, the anti-thrombogenic agent is impregnatedinto at least a portion of at least one of the catheter and the fluidcontrol device.

In a preferred embodiment, at least one of the catheter and the fluidcontrol device has a chamber for holding the anti-thrombogenic agent.

In a preferred embodiment, at least one of the catheter and the fluidcontrol device has an anti-thrombogenic treatment surface modification.

In a preferred embodiment, at least a portion of at least one of thecatheter and the fluid control device are treated with a hydrophilicagent.

In a preferred embodiment, the hydrophilic agent comprises hydrogel.

In a preferred embodiment, the hydrogel is covalently bonded to at leasta portion of at least one of the catheter and the fluid control device.

In a preferred embodiment, the hydrogel is covalently bonded to at leasta portion of at least one the catheter and the fluid control deviceusing ultraviolet light.

In another embodiment, the present invention provides a method ofshunting cerebral spinal fluid in a patient. A catheter is placed toallow cerebral spinal fluid to flow through the lumen. At least aportion of the catheter is subjected to an anti-thrombogenic treatment.

In another embodiment, the present invention provides a method ofshunting cerebral spinal fluid in a patient. A fluid control device isplaced to allow cerebral spinal fluid to flow through the fluid passage.A catheter is placed with a lumen in fluid communication with the fluidpassage to allow cerebral spinal fluid to flow through the lumen. Atleast a portion of at least one of the flow control device and thecatheter is subjected to an anti-thrombogenic treatment.

In a preferred embodiment, the subjecting step delivers ananti-thrombogenic agent to at least a portion of at least one of theflow control device and the catheter.

In a preferred embodiment, the delivering step holds theanti-thrombogenic agent in a bioresorbable matrix.

In a preferred embodiment, the delivering step impregnates at least aportion of at least one of the flow control device and the catheter withthe anti-thrombogenic agent.

In a preferred embodiment, the subjecting step holds theanti-thrombogenic agent in a chamber separate from the lumen of thecatheter.

In a preferred embodiment, the subjecting step provides at least aportion of at least one of the flow control device and the catheter withan anti-thrombogenic treatment surface modification.

In a preferred embodiment, the providing step treats at least a portionof at least one of the flow control device and the catheter with ahydrophilic agent.

In a preferred embodiment, the hydrophilic agent is a hydrogel.

In a preferred embodiment, the treating step covalently bonds thehydrogel to at least a portion of at least one of the flow controldevice and the catheter.

In a preferred embodiment, the treating step is accomplished withultraviolet light.

In a preferred embodiment, the subjecting step injects ananti-thrombogenic agent to a proximate area of at least one of the flowcontrol device and the catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cut-away perspective view of cerebral spinal fluid flowcontrol device implanted into the cranium of a patient;

FIG. 2 is a cross-sectional side view of a venous shunt system having ananti-thrombogenic agent administered to the system;

FIG. 3 is a cut-away side view of a catheter useful in a venous shuntsystem having an anti-thrombogenic agent associated with a bioresorbablematrix;

FIG. 4 is a cross-sectional side view of a device insertable into avenous shunt system having a dome containing an anti-thrombogenic agent;and

FIG. 5 is a cross-sectional side view of a device insertable into avenous shunt system having a separate, valve-controlled reservoircontaining an anti-thrombogenic agent along-side a clear flow chamber.

DETAILED DESCRIPTION OF THE INVENTION

Consistent and reliable drainage of cerebral spinal fluid from one areaof the body to another, e.g., from a ventricle or ventricles of thebrain to another region of the body such as the peritoneum pr sagittalsinus, can be desirable. A consistent and reliable drainage method andsystem can minimize the expense as well as trauma and inconvenience tothe patient associated with cerebral spinal fluid revision surgery andcan also lesson risk to the patient due to an inoperative cerebralspinal fluid drainage system.

FIG. 1 illustrates an embodiment of a cerebral spinal fluid shunt, ordrainage, system 10 for draining cerebral spinal fluid from one area,preferably the ventricles of brain, of the body of patient 12 to anotherarea of the body of patient 12. Cerebral spinal fluid can preferably bedrained to the peritoneum and/or atrium and, alternatively, to thesagittal sinus. Shunt system 10 may consist solely of a catheter havinga lumen to transport cerebral spinal fluid or may consist, asillustrated in FIG. 1, flow control device 14.

Flow control device 14 may be located anywhere along the path ofcerebral spinal fluid flow. For example, flow control device 14 may belocated at or near the inlet for cerebral spinal fluid, e.g., at or nearthe ventricles, or may be located at or near the outlet for the cerebralspinal fluid, e.g., at or near the peritoneum.

Alternatively, flow control device 14 may be located as illustrated inFIG. 1 along the flow path between the inlet and outlet. In particular,by way of example, flow control device 14 may be near the cranium 24.

Ventricular catheter 16, having a lumen, is connects flow control device14 to inlet location 18 in the ventricle of patient 12. It is to berecognized and understood that other locations, other than inletlocation 18, can be used. Distal catheter 20 connects flow controldevice 14 with an outlet for cerebral spinal fluid, not shown, whichpreferably is in the peritoneum. It is to be recognized and understoodthat other outlet locations can be used. Examples of other possibleoutlet locations include the atrium and the sagittal sinus.

Although not required, flow control device 14 can help alleviatecerebral spinal fluid flow differential due to different positioning ofthe body. For example, when the body is supine, the difference inelevation between the inlet of ventricular catheter 16 and the outlet ofdistal catheter 20 may be relatively small. Thus, the pressuredifferential due to elevation between the inlet and outlet may also berelatively small. This may result in a relatively small flow rate ofcerebral spinal fluid through shunt system 10.

However, when the body is erect, for example, the difference inelevation between the inlet of ventricular catheter 16 and the outlet ofdistal catheter 20 may be relatively large. Thus, the pressuredifferential due to elevation between the inlet and outlet may also berelatively large. This may result in a relatively large flow rate ofcerebral spinal fluid through shunt system 10.

The presence of a flow control device 14 in shunt system 10 can help tostabilize the rate of flow of cerebral spinal fluid through shunt system10 by limiting the higher flow rates associated with, for example, anerect position of the body. However, it is to be recognized andunderstood that the present invention has applicability regardless ofwhether or not a flow control device is actually desired and/orutilized. However, since it is envisioned that a flow control device isgenerally desirable in most circumstances, the discussion hereinafterwill be mostly based upon the inclusion of a flow control device. Theuse or inclusion of a flow control device, however, is not required.

Clogging or occluding of venous shunt system 10 may be prevented orcorrected through the use of one or more anti-thrombogenic and/or clotbusting agent or agents. The use of such agent or agents can beeffective in preventing the formation of a thrombus or in theelimination of a thrombus already formed.

The use of the term anti-thrombogenic agent refers to an agent that iseffective in preventing the coagulation or clotting of cerebral spinalfluid or other fluids in or near shunt system 10. An example of ananti-thrombogenic agent is heparin. The use of the term clot bustingagent refers to an agent that is effective in clearing already existingclots or obstructions of cerebral spinal fluid or other fluids in ornear shunt system 10. An example of a clot busting agent isStreptokinase or Urokinase. Although it is recognized that ananti-thrombogenic agent may be different from a clot busting agent,throughout this specification, including the claims, the use of theterms anti-thrombogenic agent, clot busting agent, either or both, isconsidered to refer to either agents or both agents. For the purposes ofthis invention, the terms are considered interchangeable since theirpurpose is to prevent or clear clots and/or obstructions from the pathof flow of cerebral spinal fluid in shunt system 10.

FIG. 2 illustrates a cross-sectional view of an embodiment of theinvention in which an anti-thrombogenic and/or clot busting agent isdelivered, or in a preferred embodiment, injected into flow controldevice 14. In this schematic embodiment, not drawn to scale, flowcontrol device 14 is implanted underneath scalp 22 exterior of cranium24. Ventricular catheter 16 is tunneled between flow control device 14underneath scalp 22, through burr hole 26 into ventricular space 28containing cerebral spinal fluid 30. Distal catheter 20 is also tunneledsubcutaneously between flow control device 14 and venous space 32providing an outlet for cerebral spinal fluid from ventricular space 28.

Hypodermic needle 34 containing an anti-thrombogenic and/or clot bustingagent is transcutaneously inserted with tip 36 positioned at a locationwhere the injection of an anti-thrombogenic and/or clot busting agentwould be effective in preventing or clearing an obstruction in cerebralspinal fluid shunt system 10. In a preferred embodiment illustrated inFIG. 2, tip 36 of hypodermic needle 34 is positioned within the body offlow control device 14 in order to deliver an anti-thrombogenic and/orclot busting agent to flow control device 14. The presence of ananti-thrombogenic and/or clot busting agent in flow control device 14can help avoid or clear obstructions that might otherwise jeopardize theeffectiveness and/or reliability of shunt system 10.

Alternatively, hypodermic needle 34 may be used to deliver ananti-thrombogenic and/or clot busting agent to other areas in or alongthe path of cerebral spinal fluid flow in or near shunt system 10. Asexamples, an anti-thrombogenic and/or clot busting agent may bedelivered by hypodermic needle 34 to a lumen in either of ventricularcatheter 16 or distal catheter 20 or both. In another alternativeembodiment, an anti-thrombogenic and/or clot busting agent may bedelivered by hypodermic needle 34 to an area of ventricular space 28near the inlet of ventricular catheter 16 or may be delivered byhypodermic needle 34 to an area near the outlet of distal catheter 20 invenous space 32.

It is to be recognized and understood that other delivery mechanisms andmethods, beyond the use of a hypodermic needle as illustrated in FIG. 2,are contemplated as well.

FIG. 3 illustrates an alternative delivery mechanism and delivery methodfor the delivery of an anti-thrombogenic and/or clot busting agent toshunt system 10. Bioresorbable matrix 38 is secured in the fluid flowpath of shunt system 10, for example prior to implantation.Bioresorbable matrix 38 is impregnated with an anti-thrombogenic and/orclot busting agent. Anti-thrombogenic and/or clot busting agent isgraduated released from bioresorbable matrix 38 while shunt system 10 isin use thus preventing or clearing clots which would otherwise obstructthe flow of cerebral spinal fluid through shunt system 10.

Bioresorbable matrix 38 is degraded biologically and may be constructedfrom a bioresorbable material such as the polylactic acid and lacticacid copolymers currently used in the MacroPore™ CMF™ products marketedby Medtronic, Inc., Minneapolis, Minn. In an embodiment, bioresorbablematrix 38 may be using a copolymer described in U.S. Pat. No. 4,916,193,Tang et al, Medical Devices Fabricated Totally Or In Part FromCopolymers of Recurring Units Derived From Cyclic Carbonates andLactides, the content of which is hereby incorporated be reference.

As illustrated in FIG. 3, bioresorbable matrix 38 is positioned within alumen of ventricular catheter 16. Bioresorbable matrix 38 may also topositioned a lumen of distal catheter 20 or, alternatively, may bepositioned within flow control device 14 and illustrated by flow controldevice 14A in FIG. 4.

FIG. 4 also illustrates an alternative delivery mechanism and method foran anti-thrombogenic and/or clot busting agent. Flow control device 14Ais similar to flow control device 14 having a flow chamber 40 with aninlet fluidly coupled to ventricular catheter 16 and an outlet fluidlycoupled to distal catheter 20. Also included in flow control device 14Ais a conventional fluid flow control mechanism which is not explicitlyshown. Such flow control mechanisms, such as a tortuous path, however,are well know in the art.

A preferred fluid control mechanism is illustrated in co-pending U.S.Patent Application filed on even date herewith in the names of WilliamJ. Bertrand and Bill Sugleris and entitled “Implantable Cerebral SpinalFluid Flow Device and Method of Controlling Flow of Cerebral SpinalFluid”, the contents of which are hereby incorporated by reference.

Flow control device 14A differs from flow control device 14 by having asecond chamber 42 that holds a supply of anti-thrombogenic and/or clotbusting agent.

Second chamber 42 has an opening 44 permitting communication ofanti-thrombogenic and/or clot busting agent from second chamber 42 intothe fluid flow path of shunt system 10, such as into flow chamber 40 offlow control device 14A.

In a preferred embodiment, upper dome 46 may be flexible. Since flowcontrol device 14A may be implanted subcutaneously just under scalp 22,pressure applied to scalp 22 can deform upper dome 46 forcing an amountof anti-thrombogenic and/or clot busting agent to flow from secondchamber 42 through opening 44 into flow chamber 40 where the agent oragents can operate effectively to prevent or clear clots andobstructions.

While shown as part of flow control device 14A, it is to be recognizedand understood that second chamber 42 could also be part of a deviceseparate from a device that provides flow control. That is, the flowcontrol function of flow control device 14A could be separate from theanti-thrombogenic and/or clot busting function of second chamber 42.Flow control device 14A could perform only an anti-thrombogenic and/orclot busting agent function and not a flow control function. Flowcontrol could then, optionally, be provided in a separate device alongthe flow path of shunt system 10, if desired.

FIG. 5 is a cross-sectional view of another embodiment of the presentinvention. Flow control device 14B is similar to flow control device 14Aby having flow chamber 40 providing a main fluid path for cerebralspinal fluid and second chamber 42 for holding an anti-thrombogenicand/or clot busting agent. Preferably, anti-thrombogenic and/or clotbusting agent is held in chamber 42 with a bioresorbable matrix asdescribed above with respect to FIG. 3. As with flow control device 14A,opening 44 provides a path for communication of anti-thrombogenic and/orclot busting agents from second chamber 42 to the main fluid flow pathof shunt system 10.

Flow control device 14B also has an opening or a one-way valve 48positioned between a main fluid flow path of shunt system 10, in thiscase either flow chamber 40 or ventricular catheter 16, that will allowsome of the flow of cerebral spinal fluid from ventricular catheter 16to second chamber 42 forcing some of the anti-thrombogenic and/or clotbusting agents from second chamber 42 through opening 44 into the mainfluid flow path of shunt system 10. Thus, a continuing supply ofanti-thrombogenic and/or clot busting agent is available to shunt system10 relying only on the flow of cerebral spinal fluid to dispense theanti-thrombogenic and/or clot busting agents.

Optionally a low-pressure opening valve 50 may be positioned in the flowpath of flow chamber 40. One-way valve 48 in this embodiment would havea higher, perhaps only slightly higher, opening pressure. Under normal,i.e., unobstructed, flow conditions, most or nearly all of the flow ofcerebral spinal fluid would pass through flow chamber 40 with little ornone of the flow of cerebral spinal fluid passing through second chamber42.

Upon buildup of back pressure due to downstream clotting or obstructionof cerebral spinal fluid flow in shunt system 10, one-way valve 48 willeither open or open further resulting in a flow or increased flow ofcerebral spinal fluid through second chamber 42 allowing the release, orrelease of greater amounts of, anti-thrombogenic and/or clot bustingagents.

As with flow control device 14A of FIG. 4, it is to be recognized andunderstood that second chamber 42 could also be part of a deviceseparate from a device that provides flow control. That is, the flowcontrol function of flow control device 14B could be separate from theanti-thrombogenic and/or clot busting function of second chamber 42.Flow control device 14B could perform only an anti-thrombogenic and/orclot busting agent function and not a flow control function. Flowcontrol could then, optionally, be provided in a separate device alongthe flow path of shunt system 10, if desired.

As can be seen, the anti-thrombogenic and/or clot busting agent may bedelivered to shunt system 10 in a number of different manners. Theanti-thrombogenic and/or clot busting agent may be injected, for exampleas described above with respect to FIG. 2. The anti-thrombogenic and/orclot busting agent may be held in a bioresorbable matrix, for example asdescribed above with respect to FIG. 3. The anti-thrombogenic and/orclot busting agent may be held in a second chamber, for example asdescribed with respect to FIG. 4 and FIG. 5.

An anti-thrombogenic and/or clot busting agent may also be providedthrough a surface treatment modification of one or more surfaces of anyor all of the components of shunt system 10. In particular, one or moreof the surfaces of shunt system may be made hydrophilic through the useof well known techniques and processes. In a preferred embodiment of thepresent invention, one or more surfaces of shunt system 10 is madehydrophilic through the use of hydrogel. It is preferred that thehydrogel be covalently bonded to surface of an element or elements ofshunt system 10 and still more preferably that such covalent bonding beaccomplished with ultraviolet light. Other bonding methods may also beemployed.

Suitable hydrogels include those that are 70 to 80 percent water contentby weight. In a preferred embodiment, polyvinylpyrrolidone (PVP orPovidone) is utilized. PVP is ionically neutral. In other embodiments,PEG/PEO (polyethylene glycol/polyethylene oxide), PAA (polyacrylamide)and/or PVA (polyvinyl alcohol) hydrogels may be used. Other hydrogelsmay also be employed.

Preferably, hydrogel is surface grafted using covalent bonding to theimplant surface. Coatings are held in place with Van der Waals forces,hydrogen bonding, ionic bonding or mechanical attachment. Preferably,covalent attachment, which is much stronger, is used and may beaccomplished using ultraviolet light or other methods.

This treatment is similar to ultraviolet linked polyvinylpyrrolidoneutilized under the tradename “BioGlide” by Medtronic, Inc., Minneapolis,Minn., for a surface modification of silicone elastomer shunts for thereduction of bacterial adhesion. This technology is described in U.S.Pat. No. 4,722,906, Guire et al, Binding Reagents and Methods; U.S. Pat.No. 4,973,493, Guire et al, Method of Improving the Biocompatibility ofSolid Surfaces; U.S. Pat. No. 4,979,959, Guire et al, BiocompatibleCoating For Solid Surfaces; U.S. Pat. No. 5,002,582, Guire et al,Preparation of Polymeric Surfaces Via Covalently Attaching Polymers;U.S. Pat. No. 5,217,492, Guire et al, Biomolecule Attachment ToHydrophobic Surfaces; U.S. Pat. No. 5,258,041, Guire et al, Method ofBiomolecule Attachment To Hydrophobic Surfaces; U.S. Pat. No. 5,263,992,Guire et al, Biocompatible Device With Covalently Bonded BiocompatibleAgent; U.S. Pat. No. 5,512,329, Guire et al, Surface TreatmentPreparation, and U.S. Pat. No. 5,741,551, Guire et al, Preparation ofPolymeric Surfaces, the contents of all of which are hereby incorporatedby reference.

Thus, embodiments of the anti-thrombogenic venous shunt system andmethod are disclosed. One skilled in the art will appreciate that thepresent invention can be practiced with embodiments other than thosedisclosed. The disclosed embodiments are presented for purposes ofillustration and not limitation, and the present invention is limitedonly by the claims that follow.

1. A venous shunt system adapted to shunt cerebral spinal fluid in apatient, comprising: a catheter, having: a first fluid flow lumen and asecond fluid flow lumen through which said cerebral spinal fluid flows,said first fluid flow lumen having a fluid flow lumen pressure; a firstlumen having a first lumen pressure and coupled to said second fluidflow lumen; and a second lumen coupled to said first lumen and defined,at least in part, by a second lumen wall; a low-pressure valve couplingsaid first fluid flow lumen to said first lumen, said cerebral spinalfluid flowing through said low-pressure valve when a difference betweensaid fluid flow lumen pressure and said first lumen pressure is greaterthan a pressure rating of said low-pressure valve; a one-way valvecoupling said first fluid flow lumen to said second lumen, said one-wayvalve having a higher pressure rating than said low-pressure valve andallowing at least some cerebral spinal fluid to enter said second lumenwhen said difference between said fluid flow lumen pressure and saidfirst lumen pressure is greater than said pressure rating of saidone-way valve; an anti-thrombogenic agent contained within said secondlumen, said anti-thrombogenic agent being delivered to said first lumenwhen said cerebral spinal fluid enters said second lumen; and whereinsaid second lumen is deformable when a force external to said venousshunt system is exerted on said second wall, wherein saidanti-thrombogenic agent is delivered to said first lumen when said forceis exerted on said second lumen wall.
 2. A venous shunt system as inclaim 1 wherein said anti-thrombogenic agent is delivered to a proximatearea of said first lumen.
 3. A venous shunt system as in claim 2 furthercomprising a bioresorbable matrix holding said anti-thrombogenic agent.4. A venous shunt system as in claim 2 wherein said anti-thrombogenicagent is impregnated into at least a portion of said catheter.
 5. Avenous shunt system as in claim 1 wherein at least a portion of saidcatheter has an anti-thrombogenic treatment surface modification.
 6. Avenous shunt system as in claim 5 wherein at least a portion of saidcatheter is treated with a hydrophilic agent.
 7. A venous shunt systemas in claim 6 wherein said hydrophilic agent comprises hydrogel.
 8. Avenous shunt system as in claim 7 wherein said hydrogel is covalentlybonded to at least a portion of said catheter.
 9. A venous shunt systemas in claim 8 wherein said hydrogel is covalently bonded to at least aportion of said catheter using ultraviolet light.
 10. A venous shuntsystem adapted to shunt cerebral spinal fluid in a patient, comprising:a fluid control device having a fluid passage adapted to be placedallowing cerebral spinal fluid to flow through said fluid passage; and acatheter having a catheter lumen having a catheter lumen pressure, saidcatheter being in fluid communication with said fluid control device; atleast one of said catheter and said fluid control device having: a firstchamber having a first chamber pressure; a second chamber defined, atleast in part, by a second chamber wall and being fluidly coupled tosaid first chamber; a low-pressure valve, wherein said first chamber isfluidly coupled to said catheter lumen via said low-pressure valve, saidcerebral spinal fluid flowing through said low-pressure valve when adifference between said catheter lumen pressure and said first chamberpressure is greater than a pressure rating of said low-pressure valve;and a one-way valve coupling said second chamber to said catheter lumen,said one-way valve having a higher pressure rating than saidlow-pressure valve and allowing at least some cerebral spinal fluid toenter said second chamber when said difference between said catheterlumen pressure and said first chamber pressure is greater than saidpressure rating of said one-way valve; an anti-thrombogenic agentcontained within said second chamber, being delivered to said lumen whensaid cerebral spinal fluid enters said chamber via said low-pressurevalve; and wherein said second chamber is deformable when a forceexternal to said venous shunt system is exerted on said second chamberwall, wherein said anti-thrombogenic agent is delivered to said at leastone of said catheter and said fluid control device when said force isexerted on said second chamber wall.
 11. A venous shunt system as inclaim 10 wherein said anti-thrombogenic agent is delivered to aproximate area of at least one of said catheter and said fluid controldevice.
 12. A venous shunt system as in claim 11 further comprising abioresorbable matrix holding said anti-thrombogenic agent.
 13. A venousshunt system as in claim 11 wherein said anti-thrombogenic agent isimpregnated into at least a portion of at least one of said catheter andsaid fluid control device.
 14. A venous shunt system as in claim 10wherein at least one of said catheter and said fluid control device hasan anti-thrombogenic treatment surface modification.
 15. A venous shuntsystem as in claim 14 wherein at least a portion of at least one of saidcatheter and said fluid control device are treated with a hydrophilicagent.
 16. A venous shunt system as in claim 15 wherein said hydrophilicagent comprises hydrogel.
 17. A venous shunt system as in claim 16wherein said hydrogel is covalently bonded to at least a portion of atleast one of said catheter and said fluid control device.
 18. A venousshunt system as in claim 17 wherein said hydrogel is covalently bondedto at least a portion of at least one said catheter and said fluidcontrol device using ultraviolet light.